Computer-interfaced stopped-flow devices (absorbance and light-scattering), dye-laser and air-flash photolysis devices are being used to study both ligand binding rates for oxygen and carbon monoxide to diverse hemoglobins and myoglobins and subunit aggregation and dissociation rates for oligomeric hemoglobins. The latter study also entails correlating light-scattering and absorbance changes. Studies on cooperative dimeric hemoglobins and myoglobins involve determining rate constants and equilibrium constants for ligand binding and then determining whether or not these data can be accommodated by various theoretical models (Adair, allosteric, Ising, etc.). A new solid-phase method has allowed us to prepare native alpha and beta chains from diverse hemoglobins and then to synthesize various novel hybrid hemoglobins. The influence of solvent composition, temperature, amino acid substitutions and modifications, and pH on ligand-binding kinetics as well as on subunit interactions is being explored.